SQL Fundamentals

SQL, or Structured Query Language, is the go-to language for managing relational databases. It allows users to interact with databases to retrieve, manipulate, and control data efficiently. SQL provides a standardized way to define database structures, perform data operations, and ensure data integrity. From querying data to managing access and transactions, SQL is a fundamental tool for anyone working with databases.

1. Basics of SQL

• Introduction: SQL (Structured Query Language) is used for managing and manipulating relational databases.
• SQL Syntax: Basic structure of SQL statements (e.g., SELECT, INSERT, UPDATE, DELETE).
• Data Types: Different types of data that can be stored (e.g., INTEGER, VARCHAR, DATE).

2. SQL Commands

• DDL (Data Definition Language):
  • CREATE TABLE: Define new tables.
  • ALTER TABLE: Modify existing tables.
  • DROP TABLE: Delete tables.
• DML (Data Manipulation Language):
• INSERT: Add new records.
• UPDATE: Modify existing records.
• DELETE: Remove records.
• DQL (Data Query Language):
  • SELECT: Retrieve data from one or more tables. 
• DCL (Data Control Language):
  • GRANT: Give user access privileges.
  • REVOKE: Remove user access privileges.
• TCL (Transaction Control Language):
• COMMIT: Save changes.
• ROLLBACK: Undo changes.
• SAVEPOINT: Set a save point within a transaction.

3. SQL Functions

• Aggregate Functions: COUNT, SUM, AVG, MAX, MIN.
• Scalar Functions: UCASE, LCASE, MID, LEN, ROUND, NOW.

4. Joins

• INNER JOIN: Returns records with matching values in both tables.
• LEFT OUTER JOIN: Returns all records from the left table and matched records from the right table.
• RIGHT OUTER JOIN: Returns all records from the right table and matched records from the left table.
• FULL OUTER JOIN: Returns records when there is a match in either left or right table.
• CROSS JOIN: Returns Cartesian product of the two tables.
• SELF JOIN: Joining a table with itself.

5. Subqueries

• Single row subqueries: Return only one row.
• Multiple row subqueries: Return multiple rows.
• Correlated subqueries: Subqueries that refer to the outer query.

6. Indexes

• Creating Indexes: Improve the speed of data retrieval.
• Dropping Indexes: Remove indexes when no longer needed.

7. Views

• Creating Views: Virtual tables created by a query.
• Updating Views: Modifying data through views.
• Dropping Views: Removing views.

8. Constraints

• NOT NULL: Ensures that a column cannot have a NULL value.
• UNIQUE: Ensures all values in a column are unique.
• PRIMARY KEY: Uniquely identifies each record in a table.
• FOREIGN KEY: Ensures referential integrity between tables.
• CHECK: Ensures that the values in a column satisfy a specific condition.
• DEFAULT: Sets a default value for a column.

9. Transactions

• ACID Properties: Atomicity, Consistency, Isolation, Durability.
• Isolation Levels: READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, SERIALIZABLE.

10. Advanced Topics

• Stored Procedures: Precompiled collections of SQL statements.
• Triggers: SQL code that automatically runs in response to certain events on a particular table or view.
• Cursors: Used to retrieve, manipulate, and navigate through a result set row by row.
• CTE (Common Table Expressions): Temporary result set defined within the execution scope of a single SELECT, INSERT, UPDATE, or DELETE statement.
• Window Functions: Perform calculations across a set of table rows related to the current row.

11. Performance Optimization

12. Security

• User Management: Creating and managing database users.
• Role Management: Defining and assigning roles and permissions.
• Data Encryption: Techniques to secure data storage and transmission.

This overview covers the foundational and advanced topics of SQL, providing a structured path for learning and mastering SQL.